Drug dependence is acknowledged by the scientific and medical communities as a chronic disease that may require long-term, possibly lifetime management. The costs of drug abuse have increased an average of 5.3 percent per year from 1992 through 2002, reaching an estimated $180.9 billion in 2002. These costs are due in part to the elevated risk of HIV transmission associated with injection drug abuse. It is estimated that some 2.1 million Americans are receiving some form of drug abuse treatment; however longitudinal studies indicate that addicted individuals often cycle through periods treatment, abstinence, and relapse, during which the risk of HIV transmission and mortality are highest. The concept of recovery from drug addiction remains without clear definition or understanding of its etiology. Relative to onset, maintenance, and relapse, deceleration and cessation are the least studied phenomena in drug abuse research. The benefits of long-term abstinence may include decreased risk of mortality, decreased crime, increased productivity, and decreases in the risk of HIV transmission. The processes constituting recovery can be framed in the context of a drug use career, which UCLA Integrated Substance Abuse Programs (ISAP) investigators have argued needs to be studied through longitudinal, dynamic conceptual and analytic approaches. Exploratory analyses conducted by Dennis et al. (2005) suggest that multiple episodes of care over several years are the norm and that rather than thinking of multiple episodes in terms of cumulative dosage, it might be better thought of as further evidence of chronicity and of treatment system deficiencies and that further development and evaluation models of longer term recovery management is essential. Recurrent event analysis is an emerging innovative methodology that is well suited to identify the determinants of each of the stages of recovery from drug abuse, including regular use, treatment, relapse and abstinence and their attendant behaviors. Our specific aims include analyses on the determinants of durations of: (a) alternating periods of drug treatment and relapse among opioid users; (b) successive periods of drug use frequency in single-drug users (c) parallel durations of drug use among multiple-drug users; and (d) joint analysis of the cumulative and acute effects of recurrent durations of drug treatment on morbidity and mortality. In each case, the modifying effect of HIV infection on the course of recovery from drug abuse. We expect to generate new insights into the course and determinants of recovery from illicit drug dependence that can be used in policy development and in clinical practice to identify promising leverage points for re-engineering interventions in ways that shorten the relapse-treatment-recovery cycle, to increase the long-term effectiveness of treatment and decrease the incidence of HIV/AIDS.